Silver bullet for my nausea-inducing monitor?

February 13, 2007 6:37 PM

[DirtyPowerFilter] My CRT monitor has developed a nasty shake/vibration at certain refresh settings, since I moved to a new apartment. I think the problem stems from the old electrical system. Is there anything I can do to "clean" the power and alleviate the problem? Or are all "power conditioning" products bogus? Backstory and more info below the fold.

So I just recently moved into a new apartment, in an older (1940s or 50s) building with original wiring. The building has all 2-prong outlets. I got my computer all set up, using a 2-prong to 3-prong grounding adaptor, properly attached to the center screw of the old-style 2-prong outlet.

However, my trusty old 20" CRT monitor isn't happy. When it's set to 75Hz refresh (my preferred setting), it jitters and shakes horribly. At 60Hz, no problem -- it's rock solid (but it gives me headaches). At lower resolutions and higher refresh rates, like 80Hz and above, it also seems stable. Unfortunately, the lower resolutions keep me from using some applications, and really cramp my desktop. I've tried degaussing, to no effect.

I have done some research, including this older AskMe question on shaky CRT images, but I think that my problem stems from the power (and/or bad grounding), and not from nearby electromagnetic fields (since I can turn off everything else in the house and still have the problem, or move the monitor around and not see any difference. The computer is located in the outside corner of the building on the second floor; there's nothing motorized or mechanical nearby, or on the same circuit (at least not inside my apartment). It's possible there's something big and nasty elsewhere on the building's electrical system, but if that's the case it's beyond my control, and I have to figure out how to deal with it.

At the resolution I use my monitor at, the only options are 60Hz or 75Hz. So it's either jitter at 75, or headaches at 60. I'm trying to think of solutions. Obviously, ditching the CRT in favor of an LCD (which we have on other computers, and seem to work fine) is one, but I'd rather not -- first, because it means money, and second, because my CRT monitor is pretty nice, and I don't like the limited color gamut of LCDs for photo and video work. Modifying the wiring in the apartment is probably out, or at least a definite last-resort option (since it would entail going through the landlord, etc.). Similarly, running a separate ground wire would be difficult -- I've thought of getting some heavy copper braid and running it to the CW pipe in the bathroom, but I'm afraid that would just create big loop.

Are there any sort of 'power conditioner' products that might help? Optimally, I'd like something that I could plug in between the wall and the monitor, which would isolate it from whatever junk is coming in, and let it play nice at 75Hz again. I've seen such products aimed at audiophiles with a lot of extra money to spend, but I've always been suspicious that they're nothing but electronic snake oil. Do such things exist at less exorbitant prices, and do they actually work?

Other suggestions would be welcome also, if there's some possibility I haven't thought of.

posted by Kadin2048 to computers & internet (16 comments total)

The power conditioners that will help are built into higher-end uninteruptable power supplies, or UPSes. You can pick them up for about $150 at any computer or office supply store, just make sure it has an "always online power conditioner" or some such.
posted by SpecialK at 6:55 PM on February 13, 2007

(But it may be cheaper to buy an LCD monitor. Seriously. My eyesight has gotten BETTER since I ditched all the CRTs in my life.)
posted by SpecialK at 6:56 PM on February 13, 2007

I can see why you'd be wary of power conditioners - anything aimed towards the audiophile crowd should be approached with a HUGE degree of caution. That said, as an Audio Professional (which is the reason I'm NOT an audiophile), I love power conditioners. They're a must in any sort of situation where a line might spike, or otherwise be "dirty."

Not being an electrical engineer or an electrician, I can't say whether you've got a dirty line or grounding problems. If you can find a place that'd rent you a power conditioner (often comes with a rack of audio gear), you could rent it for 1 day, and see how much it helps. That'd run you probably $20 or less, from a reputable audio rental company.

Alternatively, I think that a lot of UPSes have line conditioning built-in. I'm sure someone here knows whether that's the truth, and could probably point you at particular models. And there's always the Google.

On preview, there's SpecialK to beat me to it.


Reduces noise by up to 40db my ass. You want to know what reduces noise by 40db? Neve. Jackasses!@
posted by god hates math at 6:58 PM on February 13, 2007

In two places I've worked, I've seen problems with CRT's caused by proximity to the building power entrance. Note that this kind of thing will not be helped by a power conditioner.

I'm with the others: LCDs are good and cheap these days.
posted by oats at 7:23 PM on February 13, 2007

The screw in the centre of the old powerpoint is likely not grounded properly or at all, hence the 3-prong adapter does nothing. Not a good situation to be in: your computer relies on the ground for safety because there are exposed metal parts.

The computer and monitor are plugged into the same powerpoint via a power-board, right? If they're in different outlets with grounds, particularly if those outlets are on different cable runs, you can have HUGE ground loops that could cause issues.

Have you tried running it (PC+monitor) from a different powerpoint, i.e. one from another room entirely? Might be better ground connection there. When I was in CA for 3mo, the apartment I rented had ONE grounded outlet, so I ended up running a 20m heavy duty extension lead and putting the computer on that.

Ignore "audiophile" power conditioners, they're nothing useful even to audiophiles, unless you include "people unusually susceptible to the placebo effect" in the set "audiophiles". An online (always inverting, no direct connection between line and load) UPS may solve your problem but you must be ABSOLUTELY sure that it is correctly grounded; the 2/3-prong adapter does not count as such.
posted by polyglot at 7:26 PM on February 13, 2007

When I see shaky CRT images in schools, they're invariably caused by a nearby wall wart or power brick, usually for a printer or speakers. Those things are surrounded by surprisingly strong magnetic fields at mains frequency, and putting one near the deflection coils at the back of the CRT will definitely make the picture wobbly.

I know you said you can turn off everything else in the house and still have the problem, but I'm thinking you're probably not turning off your computer and/or minor stuff connected to it, or you wouldn't be able to see an image to notice it's shaking.

So if your monitor and computer have a different physical arrangement at your new place to what they had at the old place, and especially if there are little power supplies that are closer to the back of the CRT than they used to be, move those.

Power conditioners are unlikely to help you, because the wobble you're seeing is a 15Hz beat between the mains electricity's 60Hz and your refresh rate's 75Hz. Cleaning up the 60Hz and making it all pure and nice won't remove that beat.

If it's not magnetic interference from something nearby, it's a grounding problem; you've got part of the 60Hz mains signal finding its way into the monitor where it shouldn't be. Try temporarily disconnecting the grounding screw on your 2- to 3-pin adapter and see if that makes any difference at all (even a slight difference). If it doesn't, it's highly likely that the plate that the grounding screw is screwed into is not, in fact, grounded, and that the grounding screw isn't achieving its intended purpose.

If the building wiring is really dodgy, the grounding screw might even be connected to the hot side of the mains supply. Before you spend money on a power conditioner, spend money on having a competent sparky come in and check out your wiring.
posted by flabdablet at 7:39 PM on February 13, 2007

kadin2048,

You've done a lot of work and your post has much more info than the typical "I've got a wierd problem" post.

You've also gotten good advice from these folks, and I have little to contribute that will improve on it, much.

I would like to suggest that the first step in isolating problems is repeatability. You seem to have nailed that. You also seem to have eliminated local EMI from other sources. You've removed some of the positional stuff, and you've pretty much given the monitor a clean bill of health.

I know of nothing on the power lines that's going to do this. I CAN see how a missing ground might.

Were I troubleshooting it, I'd concentrate on making the problem go away first. In almost all old houses, there are outlets that have been converted to 3 wire. Check your kitchen, basement and bathroom. Find one. It will have a legit ground. If you don't have one, ask a neighbor. Somebody has a GFCI in the bathroom or kitchen. Check your refrigerator outlet.

Move the unit there and try it out. If the problem goes away, take it back to the original outlet and see if it is still present. If so, blame the ground.

Once you can do that, you are 90% of the way there. Don't waste time or money fixing the ground until you prove you have a problem with it.
posted by FauxScot at 7:55 PM on February 13, 2007

I have had precisely this problem... nasty shimmer/wave at 75Hz, fine at other frequencies. (an expensive Sony monitor, fwiw) I believe, as you do, that it was caused by crappy electrical wiring. Fortunately, I was able to go to 85Hz, which straightened it out, but it sounds like that won't work for you.

I can tell you that an APC UPS, which is not 'always on', did not eliminate the problem. An always-on power protector, like a Siebel unit, might potentially work; they convert AC to DC and back to AC again, all the time, so you get very clean power that's isolated from the rest of the house. But they're pretty expensive.

As SpecialK suggests, just switching to an LCD might be a solution for you. The Dell 2407s, monstrous 24" beasts, are down to the $750 range if you watch for sales, and are excellent monitors.

At this point, there's only two real drawbacks to LCDs... the color reproduction isn't as accurate as a CRT's, and there's a frame or two of input lag, which can mess you up a little if you're a high-end FPS player. If you're not a graphic professional or a VERY good gamer, LCDs are just flat better for almost everything. And they're TREMENDOUSLY nicer to stare at all day.
posted by Malor at 8:31 PM on February 13, 2007

(Dell also has good 20" screens, too, in the $350 range, if $750 is too much. I'm not fond of their computers, but they make good monitors.)
posted by Malor at 8:33 PM on February 13, 2007

I got my computer all set up, using a 2-prong to 3-prong grounding adapter, properly attached to the center screw of the old-style 2-prong outlet.

From the article you link:

If the electrical box is not grounded, connecting the wire really serves no purpose since it will not be connected to anything.

Do you know for certain that the screw (and hence the electrical box) is grounded? As others have said, this is important.

the only options are 60Hz or 75Hz ... second, because my CRT monitor is pretty nice

This doesn't compute. A CRT with 75Hz refresh rate is pretty poor.



You have a lot of electronics gear running fine, so the AC can't be that bad.. You do have to address the grounding issue - even if that only means knowing for certain if you are grounded or not. There are tons of old AskMe questions on this very frustrating topic (frustrating for those stuck with old wiring, of course).

To fix your monitor, find a way to get it to run at a higher refresh rate:

1. Check that your refresh rates aren't being limited by a software problem. For example, if Windows (if you are running windows) detects the monitor incorrectly, it can sometimes block out compatible modes. Also, monitors are often capable of operating at higher "unsupported" modes, so you might as well try forcing the refresh rate higher to see what happens.
2. Check that your video adapter is capable of driving a higher mode. If the video card is limiting the display capability, get a new one, they are cheap.
3. Check Craigslist for a late model trinitron, like a professional series monitor from Compaq or Dell. You should be able to get one for free, but certainly not more than $25 for 17" and $75 for 21".

To assist in most of those steps, and also to determine how much the AC is contributing to your problem, you should try to borrow a CRT for testing in your apartment, before you buy anything.
posted by Chuckles at 9:41 PM on February 13, 2007

Power conditioners actually work. Even the $50 ones. Most of them are rack-mountable 8 or 10 outlet units aimed at the DJ market, but they should clean up your power for a monitor too.
posted by fvox13 at 10:24 PM on February 13, 2007

Thanks, everyone who's helped out so far. I made a few discoveries this morning.

Disconnecting the ground lead from the 3-prong to 2-prong adapter didn't seem to have any effect, on anything. This makes me suspect that perhaps the center screw in the wall outlet really isn't grounded.

While doing this, I had a DMM out (in order to make sure the center screw wasn't hot) and noticed a few other odd things. When unloaded, hot/neu are around 120.0VAC RMS (as they should be). However, when I hook up all the equipment, it sags to around 118.5V. Also, at no load, the grounding screw and neutral have no AC or DC difference....but loaded up (and with the screw it attached to the third prong of the cable running to the computers), there's a 9VAC difference between them. Not sure if any of this is significant, or of any of it would tend to confirm or deny a theory of bad grounding, but I'm starting to think in that direction. If the ground is just hanging, maybe it's acting like a big antenna and funneling a lot of 60Hz back into my gear.

I spied a GFCI receptacle under the sink in a bathroom, so I'm off to find a nice heavy-gauge extension cord, and see if plugging into that does anything. I'll report back!

As for the monitor and its apparent lack of refresh rates, I'm not sure what to say. At 1280x1024, the only ones offered by my Mac are 60Hz and 75Hz. On investigation, I think it's probably possible to force it higher, since I think that the Mac's System Preferences are very conservative, and the specs on the monitor make me believe it could go higher. But I'm hesitant to just force it to a higher refresh, if that's just going to mean ignoring a grounding problem that might crop up elsewhere.
posted by Kadin2048 at 7:42 AM on February 14, 2007

I wouldn't put it completely on the power source, either. I remember a dorm room I was in back in college that had the fun effect of making my monitor distort on one side of the room. It had nothing to do with the power outlets on that side of the room, but of the actual geography of the room -- I have no idea what was creating such a magnetic field, but it was happening. As soon as I moved my desk to the other corner, it was fine.
posted by mikeh at 8:20 AM on February 14, 2007

Disconnecting the ground lead from the 3-prong to 2-prong adapter didn't seem to have any effect, on anything. This makes me suspect that perhaps the center screw in the wall outlet really isn't grounded.

It means that the possible ground connection isn't helping any potential electromagnetic interference problems, but that is really the only thing you can conclude. It could very well be grounded, but just not having a noticeable effect.

When unloaded, hot/neu are around 120.0VAC RMS (as they should be). However, when I hook up all the equipment, it sags to around 118.5V. Also, at no load, the grounding screw and neutral have no AC or DC difference....but loaded up (and with the screw it attached to the third prong of the cable running to the computers), there's a 9VAC difference between them.

The sag to 118.5 V is reasonable enough.

Assuming the ground was real, neutral and ground should be similar but not identical (they would be identical if there was no electrical load anywhere in the building). Adding the load should change the neutral-to-ground voltage by half the amount that the neutral-to-live voltage sags, so a 9V difference seems wrong..

I'd suspect that there is no ground connection, and that the 9V is coming from leakage current within the loads. This could be confirmed by measuring the neutral to ground voltage when the grounding tab on the adapter is not connected to ground in any way (put some electrical tape over the screw, or whatever, to guarantee isolation).

Please be very careful with this testing! Keeping one hand behind your back is always a good precaution. And doing this testing while standing up in rubber souled shoes is good too. Both of these things help to insure that you don't inadvertently complete a circuit. I know, I know, you've gotten this far already.. Still :)

I spied a GFCI receptacle under the sink in a bathroom, so I'm off to find a nice heavy-gauge extension cord, and see if plugging into that does anything. I'll report back!

GFCI itself isn't going to do anything for your issue, of course, but there is a chance that the outlet is actually grounded..


Go on, force the refresh higher, you know you want to!
posted by Chuckles at 9:26 AM on February 14, 2007

Some more tests: I ran out to Home Depot and picked up an extension cord, and a Sperry plug-in outlet tester.

The tester revealed that something is up with the outlet that I was using the computer out of. With the grounding adapter connected, the Sperry gave inconclusive results (literally; it flickered between "OK" and "open ground"). So the ground there is not solid.

The tester confirmed that the GFI receptacle in the bathroom, however, does seem to be wired correctly. So I ran an extension cord from that, into the computer room, and plugged things in there. (Drumroll, please...) And the problem still occurred.

Also, I decided to test the voltages of the old outlet, under load, against the ground from the GFI outlet as a reference. The old outlet has a hot of 118-120V, neutral of 0, and ground of 10V (that's ten volts AC, according to the meter, I triple-checked because I didn't believe it at first).

So it now seems that I have two separate issues. In addition to whatever was originally wrong with my CRT, I now have an electrical outlet with grounding issues, that I think is going to demand professional attention.
posted by Kadin2048 at 10:45 AM on February 14, 2007

It's possible your monitor may simply have something wrong with it; maybe something got damage internally during the move. When I first read your question I was a bit suspicious that it was due to your electrical supply. To completely rule that out you'd have to take it to a friend's house, preferably with your computer. If you like the monitor maybe you can find the same model free/cheap; used CRTs are worth very little these days.

I'd talk to your landlord about the outlet.
posted by 6550 at 4:20 PM on February 14, 2007